Lighting unit and image scanner using same

ABSTRACT

A lighting unit includes LED chips positioned in an array form in a main scanning direction on LED substrates. Cylindrical parabolic mirrors each form a shape in which a cylindrical paraboloid having curvature with respect to an sub-scanning direction has been clipped by an axial plane that is perpendicular to the vertex of the cylindrical paraboloid in the main scanning direction, and project light emitted from the light source on an illumination area of an illuminated item. Each cylindrical parabolic mirror includes an anchoring section that is provided at the vertex of the cylindrical paraboloid, and extends from the vertex in an outside direction of the cylindrical paraboloid. Heat-radiating plates each have a contact section that is in contact with the LED substrate, and a non-contact section. Each LED substrate is interposed between the contact section of the heat-radiating plate and the anchoring section of the cylindrical parabolic mirror.

TECHNICAL FIELD

The present invention relates to a lighting unit for accomplishinglinear lighting of scanned items, such as printed material or bookmanuscripts, and to an image scanning device using this lighting unit.

BACKGROUND ART

Image scanning devices are used in copiers, scanners, facsimiles and/orthe like. The image scanning device is a device for scanning an entireimage by scanning the image in a scanning position using aone-dimensional imaging element, and is provided with a lighting unitfor accomplishing lighting when reading an original. In the imagescanning device, it is necessary to scan the image information with goodaccuracy and at high speed, so a lighting unit composition has beendisclosed for uniformly lighting the original with high efficiency. Asgeneral expressions, the direction in which a one-dimensional imagingelement is arrayed is called the main scanning direction, and thedirection of scanning is called the sub-scanning direction. In addition,the direction orthogonal to both the main scanning direction and thesub-scanning direction is called the focal depth direction in a scanningoptical system and is called the lighting depth direction in a lightingunit.

The document lighting unit disclosed in Patent Literature 1 is providedwith point light sources such as multiple LEDs (Light Emitting Diodes)arranged in the main scanning direction. The direction in which light isemitted from these point light sources is roughly parallel to the normaldirection to the document stand on which a document is loaded and is inthe opposite direction from the document stand. Light from these pointlight sources is guided to the document surface as lighting light bymultiple reflective surfaces arranged facing the point light sources.

The condensing lighting device disclosed in Patent Literature 2 isprovided with a light source positioned at the focal position of areflective surface on a parabola, and a lens having two types ofcurvature for condensing light from the light source and light from thereflective surface.

The document lighting device disclosed in Patent Literature 3 isprovided with LED elements disposed along the main scanning direction,and a reflective plate surrounding the LED elements. The shape of thisreflective plate is a parabolic two-dimensional curve.

Patent Literature 4 discloses the composition of a light guide, lightingunit and image-scanning lighting device capable of realizing lightingwith high illumination, large lighting depth and broad lighting width inthe sub-scanning direction.

Patent Literature 5 discloses an image scanning device in which acircuit substrate on which light-emitting diodes are provided isanchored to a metal support section, and the support section iscarriage-anchored.

CITATION LIST Patent Literature

-   -   Patent Literature 1: Unexamined Japanese Patent Application        Kokai Publication No. 2010-199875 (FIGS. 1-9)    -   Patent Literature 2: Japanese Patent Official Announcement No.        H4-15457 (FIGS. 1-3)    -   Patent Literature 3: Unexamined Japanese Patent Application        Kokai Publication No. 2005-234108 (FIGS. 1, 2)    -   Patent Literature 4: Unexamined Japanese Patent Application        Kokai Publication No. 2009-272215 (FIG. 3)    -   Patent Literature 5: Unexamined Japanese Patent Application        Kokai Publication No. 2007-306309 (FIG. 4)

SUMMARY OF INVENTION Technical Problem

In the image scanning device, it is necessary to have a lighting devicewith a large lighting depth when utilizing a scanning optical systemhaving a large focal depth enabling clear imaging of images of scannedobjects having unevenness on the surface, such as book manuscripts orwrinkled paper money. When scanning documents having unevenness,fluctuations in the brightness of the scanned images occur when there isa brightness distribution in the lighting depth direction.

The document lighting unit disclosed in Patent Literature 1 comprisesmultiple reflective surfaces, so the angular component of the lightinglight rays toward the document surface from the respective reflectivesurfaces with respect to the document stand has multiple peaks. As aresult, it is difficult to achieve lighting with uniform illumination ofa document whose distance from the document stand changes, such as abook manuscript and/or the like.

With the lighting device disclosed in Patent Literature 2, it ispossible for the lighting light rays to approach parallel light rays asa result of a combination of parabolas and lenses, so lighting withuniform illumination is relatively easy on documents in which thedistance from the document stand changes, such as book manuscriptsand/or the like. However, the lighting device disclosed in this PatentLiterature comprises a parabolic reflective mirror and lenses having twotypes of curvature, so the size of the optical system becomes large andcompactness of the lighting device is difficult to realize, and costalso becomes an issue.

With the lighting device disclosed in Patent Literature 3, the LEDelements are lined up in the main scanning direction, reflective platessurrounding the LED elements are provided and the shape of thereflective plates is a parabolic two-dimensional curve. Consequently itis possible for the lighting light rays to approach parallel light rays,so that lighting with uniform illumination is relatively easy ondocuments such as book manuscripts and the like whose distance from thedocument stand changes. However, in order to provide the reflectiveplates surrounding the LED elements, the optical system becomes largeand making the lighting device compact becomes difficult.

In Patent Literature 4, a composition is disclosed in which parallellight rays are produced using a light guide.

In Patent Literature 5, an image scanning device is disclosed in which acircuit board on which light-emitting diodes are provided is anchored toa metal support member and the support member is carriage-anchored. Inthe case of this kind of composition, heat emitted by the light-emittingdiodes is discharged toward the carriage via the support member, so thetemperature of the carriage rises and the temperature of otherelectronic components provided on the carriage rises. As a result, theproblem existed that deterioration of performance occurs.

It is an objective of the present invention to provide ahigh-illumination lighting unit and image scanning device that controltemperature increases in the light source and/or the like caused by heatdischarged from the light source while having large lighting depth.

Solution to Problem

The lighting unit according to the present invention comprises:

a light source in which light-emitting elements are positioned in anarray in a main scanning direction;

a light source substrate that is a substrate extending in the mainscanning direction and comprises a light-emitting element mountingsection on which the light source is disposed and a non-light-emittingelement mounting section extending from the light-emitting elementmounting section in a direction orthogonal to the main scanningdirection;

a parabolic mirror forming a shape in which a cylindrical paraboloidhaving curvature with respect to an sub-scanning direction has beenclipped by an axial plane that is perpendicular to the vertex of thecylindrical paraboloid in the main scanning direction, provided with ananchoring section provided at the vertex of the cylindrical paraboloidand extending in the outside direction of the cylindrical paraboloidfrom the vertex, and projecting light emitted from the light source onan illumination region of an illuminated item; and

a heat-radiating plate extending in the main scanning direction andpossessing a contact section that is in contact with the surfaceopposite the surface on which the light-emitting elements of the lightsource substrate are mounted, and a non-contact section;

wherein the light source is positioned so as to include the focalposition of the cylindrical paraboloid in the light-emitting region oflight, the central axis in the light-emitting direction of the lightbeing perpendicular to the axial plane; and

the non-light-emitting element mounting section of the light sourcesubstrate is interposed between the contact section of theheat-radiating plate and the anchoring section of the parabolic mirror.

Advantageous Effects of Invention

With this invention, lighting of a document by roughly parallel lightrays is possible, so it is possible to efficiently light documents. Inaddition, changes in the light quantity are small in the lighting depthdirection, so it is possible to obtain bright images even when thedistance to the document is distant. Furthermore, by positioning thiskind of lighting unit on both sides of the optical axis of a scanningoptical system, linear lighting having large lighting depth anduniformly strong distribution even in the sub-scanning direction isobtained.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view showing an image scanning device accordingto a first preferred embodiment of the present invention;

FIG. 2 is a drawing showing a parabolic shape equating to thesub-scanning direction cross-sectional shape of a cylindrical parabolicmirror;

FIG. 3 is a light path diagram of the sub-scanning directioncross-section of the lighting unit according to the first preferredembodiment of the present invention;

FIG. 4 is an example of an sub-scanning direction illuminationdistribution according to the first preferred embodiment of the presentinvention;

FIG. 5 is a sub-scanning direction cross-section of a lighting unitaccording to a second preferred embodiment of the present invention;

FIG. 6 is a structural diagram of a white LED obtaining white light byblending secondary luminescence through yellow fluorescent material witha blue light-emitting diode as the light source, with (a) being a viewfrom the LED light-emission direction along the central axis thereof,and (b) being a cross-sectional view taken along line A-A′ in (a) ofFIG. 6;

FIG. 7 is a sub-scanning direction cross-sectional view of a lightingunit according to a third preferred embodiment of the present invention;

FIG. 8 is a drawing showing the arrangement direction of an LED arrayaccording to the third preferred embodiment of the present invention;

FIG. 9 is an example of the sub-scanning direction illuminationdistribution according to the third preferred embodiment of the presentinvention;

FIG. 10 is a sub-scanning direction cross-sectional view of a lightingunit according to a fourth preferred embodiment of the presentinvention;

FIG. 11 is an example of the sub-scanning direction illuminationdistribution according to the fourth preferred embodiment of the presentinvention;

FIG. 12 is a cross-sectional view of a lighting unit according to afifth preferred embodiment of the present invention;

FIG. 13 is a detailed view of the light rays and a cylindrical parabolicblock according to the fifth preferred embodiment of the presentinvention;

FIG. 14 is a perspective view of an image scanning device according to asixth preferred embodiment of the present invention;

FIG. 15 is a light path diagram of the sub-scanning directioncross-section according to the sixth preferred embodiment of the presentinvention;

FIG. 16 is a light path diagram of the sub-scanning directioncross-section according to a seventh preferred embodiment of the presentinvention;

FIG. 17 is an example of the sub-scanning direction illuminationdistribution according to the seventh preferred embodiment of thepresent invention;

FIG. 18 is a cross-sectional view of a lighting unit according to aneighth preferred embodiment of the present invention;

FIG. 19 is a sub-scanning direction cross-sectional view of a lightingunit according to a ninth preferred embodiment of the present invention;

FIG. 20 is a perspective view of a lighting unit according to a tenthpreferred embodiment of the present invention;

FIG. 21 is a drawing showing the illumination distribution of the mainscanning direction end according to the tenth preferred embodiment ofthe present invention;

FIG. 22 is a perspective view of an image scanning device according toan eleventh preferred embodiment of the present invention;

FIG. 23 is a sub-scanning direction cross-sectional view of a lightingunit according to the eleventh preferred embodiment of the presentinvention;

FIG. 24 is a sub-scanning direction cross-sectional view of a lightingunit according to a twelfth preferred embodiment of the presentinvention; and

FIG. 25 is a sub-scanning direction cross-sectional view of an imagescanning device according to the twelfth preferred embodiment of thepresent invention.

DESCRIPTION OF EMBODIMENTS

Below, the preferred embodiments of the present invention are describedwith reference to the drawings Compositional parts that are the same orsimilar in each drawing are labeled with the same reference signs.

First Preferred Embodiment

FIG. 1 is a perspective view of an image scanning device according to afirst preferred embodiment of the present invention. The image scanningdevice comprises a top glass sheet 3, a lighting unit 2 and an imagingoptical system 1. The top glass sheet 3 is a transparent glass sheet forsupporting a scanned item (illuminated item) such as a document 7 and/orthe like. The lighting unit 2 is a unit for accomplishing linearlighting of a surface of the document 7. The imaging optical system 1 isa unit for imaging light from the document 7 in an imaging element 40.

To facilitate understanding, the direction of scanning the documentthrough electrical scanning of the imaging element 40 shall be calledthe main scanning direction 11, the direction in which the document 7moves relative to the image scanning device shall be called thesub-scanning direction 12 and the direction perpendicular to the mainscanning direction 11 and the sub-scanning direction 12 shall be calledthe depth direction 13. Here, the depth direction 13 is such that thedirection in which the document 7 is separated from the top glass sheet3 is the positive (+) direction.

In this preferred embodiment, a composition is shown such that the imagescanning device moves and accomplishes document scanning with thedocument 7 in an anchored state, but conversely, it would be fine tohave a composition in which document scanning is accomplished by movingthe document 7 with a drum conveyor and/or the like with the imagescanning device in an anchored state.

The imaging optical system 1 is positioned along a light path facingfrom the document 7 to the imaging element 40, and comprises a lensarray and reduction optical system, and/or the like. The imaging element40 is mounted on a substrate 4 and is a line sensor constituting aphotoelectric conversion circuit for photoelectric conversion and a CMOS(Complementary Metal Oxide Semiconductor), CCD (Charge Coupled DeviceImage Sensor) and/or the like comprising the driver thereof.

The lighting unit 2 is positioned between the top glass sheet 3 and theimaging optical system 1 and accomplishes linear lighting along a scanline 8 along the x-direction to the surface of the document 7 by shininglight onto the document 7 positioned on top of the top glass sheet 3.

In addition, the lighting unit 2 comprises an LED array 220, an LEDsubstrate 230 and a cylindrical parabolic mirror 20. The LED array 220comprises LED chips 210 that are LED light sources, lined up linearly inthe main scanning direction. The LED substrate 230 is a substrate onwhich the LED array 220 is mounted. The cylindrical parabolic mirror 20is a cylindrical concave mirror that makes light emitted from the LEDarray 220 roughly parallel light rays and emits this lighting lighttoward a scan line 8.

The cylindrical parabolic mirror 20 has curvature in the sub-scanningdirection 12 and has no curvature in the main scanning direction 11.FIG. 2 shows a parabolic shape equating to the sub-scanning directioncross-sectional shape of the cylindrical parabolic mirror 20. In FIG. 2,the tangential direction at the vertex 24 of the parabola, that is tosay at y=0 and z=0, is taken as the y direction and the normal directionis taken as the z direction. The parabola is given by the followingequation (Equation 1), where f is the focal length and y=0 and z=f isthe cylindrical parabola focal position 23.

$\begin{matrix}{\left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack \mspace{509mu}} & \; \\{{z = \frac{{cy}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}y^{2}}}}}{c = {1/R}}{{f = {R/2}},{k = {- 1}}}} & \left( {{Equation}\mspace{14mu} 1} \right)\end{matrix}$

In addition, as shown in FIG. 2, the cylindrical parabolic mirror 20 isformed of only a semi-cylindrical parabola y+ 21 when the parabola isdivided at y=0 and the y+ direction is considered a semi-cylindricalparabola y+ 21 and the y− direction is considered a semi-cylindricalparabola y− 22. Here, the z axis is called the axis of the parabola, andthe surface orthogonal to the y axis and including the axis of theparabola is called the cylindrical parabola axial plane 25.

FIG. 3 shows a light path diagram of the sub-scanning directioncross-section according to the first preferred embodiment of the presentinvention. In FIG. 3, the case where the lighting unit 2 is positionedto one side of an imaging optical axis 101 is shown. In order to avoidinterference with the imaging optical axis 101, the lighting unit 2needs to be such that in general a lighting optical axis 102 is inclinedfrom the imaging optical axis 101. Furthermore, because there could beassembly errors in the lighting unit 2 and the imaging optical system 1,a lighting region 104 is a region widening in the sub-scanning direction12, and moreover, in order to cope with book manuscripts and wrinkles inand floating of the document, when the focal depth becomes larger, thelighting region 104 broadens in the depth direction 13 as well.Consequently, in the lighting unit 2 there is a certain degree of widthin the sub-scanning direction 12, and uniform, substantially parallellight rays are necessary. Furthermore, when a certain degree of width inthe sub-scanning direction 12 is secured, illumination drops and thescanning speed becomes slower, so it is necessary to improve the usageefficiency of the LED light.

Hence, with the first preferred embodiment of the present invention, anLED light-emission region 218 is positioned at a position including thecylindrical parabola focal position 23. Lighting light rays 103 emittedfrom the cylindrical parabola focal position 23 are reflected by thecylindrical parabolic mirror 20, become parallel light rays, passthrough the top glass sheet 3 and reach the lighting region 104. Acentral axis 105 in the light-emission direction of the LED ispositioned in a direction perpendicular to the cylindrical parabolicmirror 24. Because the LED's light emission intensity is at a maximum onthe central axis 105 of the light-emission direction of the LED, it ispossible for LED light to be efficiently incident on the cylindricalparabolic mirror 20.

Accordingly, with this composition, lighting light close to parallellight is efficiently obtainable, so it is possible to efficiently lightthe document 7 and it is also possible to reduce changes in lightamounts in the lighting depth direction. Consequently, even when thedistance between the document 7 and the top glass sheet 3 is distant, itis possible to obtain a bright image.

FIG. 4 shows an sub-scanning direction illumination distributionaccording to the first preferred embodiment of the present invention.FIG. 4( a) shows the sub-scanning direction illumination distributionwhen the lighting unit 2 is positioned to one side of the imagingoptical axis 101, as shown in FIG. 3. In lighting by only the lightingunit on one side, the sub-scanning direction illumination distributionis an asymmetrical distribution with respect to the sub-scanningdirection 12, and when the imaging optical axis 101 and the lightingoptical axis 102 are shifted due to assembly errors and/or the like,illumination on the imaging optical axis 101 changes. In contrast, FIG.4( b) shows the sub-scanning direction illumination distribution whenthe lighting unit 2 is positioned on both sides of the imaging opticalaxis 102. The sub-scanning direction illumination distribution becomesthe sum of the lighting light from the lighting unit 2 on both sides andthus is a symmetrical illumination distribution with respect to thesub-scanning direction 12.

Accordingly, with this composition it is possible to change illuminationin the depth direction by setting the intersection position of opticalaxes of lighting units on both sides.

It would also be fine to set the illumination distribution of lightingunits on both sides symmetrical with respect to the imaging optical axis101.

For example, when the size of the illumination region 104 is taken to be1 mm in the sub-scanning direction and 8 mm in the depth direction, andwhen the inclination θ of the lighting optical axis 102 to the imagingoptical axis 101 is 20°-30°, the focal length f of the cylindricalparabolic mirror 20 is appropriately around 10 mm to 20 mm.

Second Preferred Embodiment

FIG. 5 is an sub-scanning direction cross-sectional view of a lightingunit according to a second preferred embodiment of the presentinvention. In the second preferred embodiment of the present invention,the cylindrical parabolic mirror 20 and the LED substrate 230 arepositioned using a position-determining pin 231. Through this it ispossible to accurately align the positional relationship of thecylindrical parabolic mirror 20 and the LED light-emission region 218.As a result, the parallelism of the lighting light is maintained, it ispossible to control scattering in the lighting direction and it ispossible to reduce scattering of brightness in scanning.

Third Preferred Embodiment

FIG. 6 is a structural diagram of a white LED obtaining white light byblending secondary luminescence from yellow fluorescent material, with ablue light-emitting diode as the light source. The white LED is suchthat there are depressions in an LED package 211, a blue light-emittingdiode 212 is mounted and a yellow fluorescent material 213 is loaded soas to fill the surrounding depressions. A portion of the light emittedfrom the blue light-emitting diode 212 is emitted to the outside of theLED package 211 without change and becomes blue light comprising whitelight. In addition, the other portion of the light emitted from the bluelight-emitting diode 212 is absorbed by the yellow fluorescent materialand the yellow fluorescent material emits light in the region from greento red. This becomes green to red light that comprises white light.Accordingly, the blue light-emission region becomes the region of theblue light-emitting diode 212 and the red to green light-emission regionbecomes the entire yellow fluorescent material region. That is to say,the blue light and the red to green light have different light-emissionregions.

In order to produce parallel light rays with less divergence using thecylindrical parabolic mirror 20, it would be well to cause the center ofthe light-emission region to match the cylindrical parabola focalposition 23. However, when the light-emission regions of blue light andred to green light differ as described above, it is necessary to changethe cylindrical parabola focal position 23 depending on wavelength, butrealizing this kind of composition is difficult.

On the other hand, in observation by the inventors, it was learned thatthere is a yellow fluorescent material strong light-emission regionsurrounding the blue light-emitting diode 212. Accordingly, it is fineto think of the green to red light-emission region as being around theblue light-emitting diode 212, and in order to efficiently make light ofall wavelengths into parallel light rays, the conclusion was reachedthat it would be well to make the light-emission region of the bluelight-emitting diode 212 the standard.

FIG. 7 is an sub-scanning direction cross-sectional view of a lightingunit according to the third preferred embodiment of the presentinvention. When the LED chip shown in FIG. 6 is used, it is necessary toshine light having a broad illumination depth in the sub-scanningdirection 12 in the lighting region 104 in order to increase thelighting depth. Consequently, it is fine to use a light source with abroad light-emission region width, and it is fine for the direction inwhich LED chips 210 are arrayed in the LED array 220 to be such that theblue light-emitting diode long axis 215 matches the cylindricalparabolic mirror axial plane direction, as shown in FIG. 8.

FIG. 9 is an example of computation of the sub-scanning directionillumination distribution on the top glass sheet 3 when the center ofthe blue light-emitting diode 212 is caused to match the cylindricalparabolic mirror focal position 23. FIG. 9 (a) shows the sub-scanningdirection distribution, while FIG. 9 (b) shows the illumination changein the depth direction when the sub-scanning direction is at the centerof the lighting region. By causing the blue light-emitting diode longaxis 215 to match the cylindrical parabolic mirror axial planedirection, the illumination peak in the sub-scanning direction becomesrelatively flat and the lighting width in the sub-scanning direction iswidened. At this time, the lighting illumination 8 mm above the topglass sheet is reduced around 35% compared to the lighting illuminationon (0 mm above) the top glass sheet.

With this kind of composition, it is possible to reduce changes in thedepth direction of the sub-scanning direction illumination distributionbetween the blue light and the green to red light. As a result, it ispossible to control color spotting.

Fourth Preferred Embodiment

FIG. 10 is an sub-scanning direction cross-sectional view of a lightingunit according to a fourth preferred embodiment of the presentinvention. Compared to the above-described third preferred embodiment,the fourth preferred embodiment has a composition that further controlslowering of the lighting illumination in the lighting depth direction.In FIG. 10, the composition is such that the cylindrical parabolicmirror focal position 23 is caused to match the side of bluelight-emitting diode 212 on the cylindrical parabolic mirror vertex 24side.

With this kind of composition, the light rays emitted from the side ofthe light-emitting diode 212 on the cylindrical parabolic mirror vertex24 side are turned into parallel light rays by the cylindrical parabolicmirror 20 and are guided to the lighting region. On the other hand,light rays emitted from the side of the blue light-emitting diode 212 onthe opposite side of the cylindrical parabolic mirror vertex 24 becomelight rays 106 inclined in the sub-scanning direction from the lightingoptical axis 102 and are guided to the lighting region 104. As a result,the lighting distribution in the sub-scanning direction is such that theslope on the + side in the sub-scanning direction becomes gentle, asshown in FIG. 11( a).

Hence, the farther from the top glass sheet 3 in the depth direction,the more the peak illumination position in the sub-scanning directiondistribution moves to the sub-scanning direction positive (+) direction,following the lighting optical axis angle θ. Consequently, byappropriately setting the position of the lighting unit 2 and thelighting optical axis angle θ, it is possible to cause each position inthe depth direction on the imaging optical axis 101, as shown in FIG. 11(a), and illumination at 0 mm, 4 mm and 8 mm in FIG. 11 (a), to match.As a result, it is possible to make the lighting illumination at 8 mmabove the top glass sheet to be virtually equal compared to the lightingillumination on (0 mm above) the top glass sheet, as shown in FIG. 11(b).

Accordingly, with this composition it is possible to asymmetrically dimthe lighting illumination depth in the sub-scanning direction, so it ispossible to further reduce the amount of change in the lightingillumination distribution in the sub-scanning direction of the depthdirection of the blue light and the green to red light caused by thefact that the light-emission regions differ.

Fifth Preferred Embodiment

FIG. 12 is a cross-sectional view of a lighting unit according to afifth preferred embodiment of the present invention. The lighting unitaccording to this fifth preferred embodiment of the present inventionuses as the cylindrical parabolic mirror a cylindrical parabolic block30 that is a real block formed of transparent resin. Similar to thefirst preferred embodiment, the cylindrical parabola focal position 23is in the LED light-emission region 218. Light discharged from the LEDchips 210 is incident from the cylindrical parabolic block incidentsurface 31 to the cylindrical parabolic block 30 toward the cylindricalparabolic mirror 20, is reflected by the inner surface of thecylindrical parabolic mirror 20 and is shined on the lighting region 104from the cylindrical parabolic block exit surface 32 as substantiallyparallel light rays.

FIG. 13 shows a detailed view of the light rays and the cylindricalparabolic block 30. Consider the case in which the cylindrical parabolicblock incident surface 31 is parallel to the cylindrical parabola axialplane 25 and is positioned orthogonal to the central axis 105 of the LEDchips 210 in the light-emission direction. The cylindrical parabolicblock 30 is formed of resin and/or the like and thus has a refractiveindex higher than air. Consequently, light emitted from the LEDlight-emission region 218 when incident on the cylindrical parabolicblock 30 is refracted in the direction of the central axis 105 in thelight-emission direction of the LED chips 210 by the cylindricalparabolic block incident surface 31. As a result, the divergence angleof the cylindrical parabolic block 30 becomes narrower, arriving at thecylindrical parabolic mirror 20.

Accordingly, more light rays reach the cylindrical parabolic mirror 20than the cylindrical parabolic mirror 20 positioned in the air shown inFIG. 5 and are reflected as substantially parallel light rays, making itpossible to more efficiently use LED light. Furthermore, the cylindricalparabolic block exit surface 32 is formed in a prism shape comprising asurface substantially orthogonal to and a surface substantially parallelto the light rays reflected by the cylindrical parabolic mirror 20, soit is possible to emit light rays without changing the angle of lightrays reflected by the cylindrical parabolic mirror 20.

Sixth Preferred Embodiment

FIG. 14 is a perspective view of an image scanning device according to asixth preferred embodiment of the present invention. The image scanningdevice comprises a top glass sheet 3, a lighting unit 2 and an imagingoptical system 1. The top glass sheet 3 is a transparent glass plate forsupporting an object being scanned, such as a document 7. The lightingunit 2 is a unit for accomplishing linear lighting of the surface of thedocument 7. The imaging optical system 1 is a unit for imaging lightfrom the document 7 onto an imaging element 40.

In this preferred embodiment, the lighting unit 2 comprises an LED array220, an LED substrate 230, a light guide plate 400 and a cylindricalparabolic mirror 20. The LED array 220 comprises LED chips 210 that areLED light sources lined up linearly in the main scanning direction. TheLED substrate 230 is a substrate on which LED array 220 is mounted. Thelight guide plate 400 guides light emitted from the LED array 220 to thecylindrical parabolic mirror 20. The cylindrical parabolic mirror 20 isa cylindrical concave mirror for turning light emitted from the lightguide plate 400, that is to say light emitted from the LED chips 210 viathe light guide plate 400, into substantially parallel light rays andshining the lighting light on a scan line 8.

FIG. 15 is a light path diagram of the sub-scanning directioncross-section according to the sixth preferred embodiment of the presentinvention. The LED light-emission region 218 is positioned adjacent tothe light guide plate incident surface 40 that is one side end of thelight guide plate 400. The light guide plate 400 is a parallel planarsubstrate composed of plate-shaped transparent material extending in themain scanning direction, and the surface opposite the surface adjacentto the LED chips 210, in other words the light guide exit surface 402,is positioned at a position including the cylindrical parabola focalposition 23. The lighting light rays 103 emitted from the light guideplate exit surface 402 near the cylindrical parabola focal position 23are reflected by the cylindrical parabolic mirror 20, pass through thetop glass sheet 3 as substantially parallel light rays and reach thelighting region 104. Here, it is necessary for the lighting unit 2 to besuch that in general the lighting optical axis 102 is inclined from theimaging optical axis 101, in order to prevent interference with theimaging optical axis 101. Furthermore, because of assembly errors in thelighting unit 2 and the imaging optical system 1, the lighting region104 is a region spreading out in the sub-scanning direction 12, andmoreover in order to cope with book manuscripts and wrinkles in andfloating of the document, when the focal depth becomes larger, thelighting region 104 widens in the depth direction 13 also. Consequently,with the lighting unit 2 there is a certain degree of width in thesub-scanning direction 12 and uniform, substantially parallel light raysare necessary.

Here, with the lighting unit 2 in the sixth preferred embodiment it ispossible to set the lighting width in the sub-scanning direction 12 bycombining the width of the light guide plate exit surface 402 in thecylindrical parabolic mirror axial plane direction in addition to theinclination θ of the imaging optical axis 101 to the lighting opticalaxis 102 and the focal length of the cylindrical parabolic mirror 20. Inthe first through fifth preferred embodiments, the size of thelight-emission region of the LED was directly related to the lightingwidth in the sub-scanning direction 12, but in this sixth preferredembodiment, it is possible to set the lighting width in the sub-scanningdirection without relation to the size of the light-emission region ofthe LED. That is to say, in a white LED obtaining white light byblending secondary light emission from a yellow fluorescent materialhaving a blue light-emitting diode as a light source, even when thelight-emission regions differ between the blue light and the green tored light, by using the light guide plate 400 it is possible toaccomplish uniformity in directionality and it is possible to make thelighting widths in the sub-scanning direction match. Accordingly, it ispossible to have the same amount of change in the blue light and thegreen to red light even with respect to the change in illumination inthe depth direction.

Accordingly, with this composition lighting light that is nearlyparallel light is obtainable. Through this, it is possible toefficiently light the document and it is possible to obtain a brightimage even when the distance from the document is separated, because thelight amount change is small in the depth direction of the imagingoptical system. Furthermore, when the LED light source is a white LEDthat obtains white light by blending secondary light from a yellowfluorescent material with a blue light-emitting diode as the lightsource, because the light-emission regions differ, differences arise indirectionality between the blue light and the green to red light, butthrough the light guide plate 400, it is possible to accomplishuniformity in directionality. Through this, it is possible to make theamount by which the illumination distribution in the sub-scanningdirection changes in the depth direction the same regardless of thecolor of light.

The LED substrate 230 and light guide plate 400 are respectivelyanchored to the cylindrical parabolic mirror 20 by aposition-determining pin 231 and a light guide plate supporter 405, andthe positional relationship thereof is maintained.

Seventh Preferred Embodiment

FIG. 16 is a light path diagram of the sub-scanning directioncross-section according to a seventh preferred embodiment of the presentinvention. In this seventh preferred embodiment, a scatterer 410 isdisposed covering the light guide plate exit surface 402, adjacent tothe light guide plate exit surface 402. Here, the scatterer 410 has athin plate shape and embossing or bead application processing isimplemented on a sheet surface made of resin and/or the like. Inaddition, as the scatterer 410, it would be fine to utilize one in whichdirect embossing or bead application processing has been done on thelight guide plate exit surface 402.

FIG. 17 is an example of the sub-scanning direction illuminationdistribution (a) and the illumination change in the depth direction (b)when there is no scatterer 410 and the light guide distance of the lightguide plate 400 (the distance between the incident surface and exitsurface) is short. With the light guide plate 400, light emitted fromthe LED chips 410 is reflected by a light guide surface 403, andstandardization of directionality of the emitted light and uniformity ofthe light intensity at the light guide exit surface are accomplishedwith multiple reflections. When the light guide distance is short, thenumber of reflections by the light guide surface 403 is small and lightemitted from the light guide has a directional distribution inaccordance with the number of reflections. As a result, the sub-scanningdirection illumination distribution becomes a wavy distribution inaccordance with the above-described number of reflections in thesub-scanning direction, as shown in FIG. 17 (a), and the lighting lightproceeds in the depth direction 13 while gradually widening in thesub-scanning direction 12. Consequently, the change in illumination inthe depth direction 13 at a position 0 mm in the sub-scanning directionhas wavy changes, as shown in FIG. 17 (b). Consequently, the lightingillumination achieves non-monotone change even with white paperdocuments whose distance from the document surface to the top glasssheet 3 changes continuously. As a result, a shading distribution occursin the scanned image.

With the seventh preferred embodiment, because the scatterer 410 ispositioned covering the light guide plate exit surface 402, adjacent tothe light guide plate exit surface 402, the directional distribution ofthe light guide exit light is eased or is converted into a substantiallyeven scattering distribution by the scatterer 410. Consequently, lightthat has passed through the scatterer 410 has a smooth directionalitydistribution. As shown in FIG. 17( c), the sub-scanning directionillumination distribution is no longer a wavy distribution, and as aresult, monotone illumination changes occur in the depth direction, asshown in FIG. 17( d). Through this, it is possible to scan with amonotone density change white paper documents in which the distance fromthe top glass sheet 3 to the document surface continuously changes. Ifthere is this kind of monotone density change in the depth direction, itis possible to reproduce the original density distribution of thedocument with simple corrections.

Eighth Preferred Embodiment

FIG. 18 is a cross-sectional view of a lighting unit according to aneighth preferred embodiment of the present invention. With the lightingunit according to the eighth preferred embodiment of the presentinvention, a cylindrical parabolic block 30, which is a solid block inwhich a cylindrical parabolic mirror 20 is made of transparent resin,and a light guide plate 400 are formed as a single body. Similar to theeighth preferred embodiment, the cylindrical parabola focal position 23is at the exit surface 402 of the light guide plate 400. Hence, thelight guide exit surface 400 is equivalent to the joining position ofthe light guide plate 400 and the cylindrical parabolic block 30.Because the cylindrical parabolic block 30 and the light guide plate 400are formed as a single body as described above, the light guide exitsurface 402 does not exist as a physical surface. Light emitted from theLED chip 210 is incident on the light guide plate 400, passes throughthe light guide exit surface 402 toward the cylindrical parabolic mirror20 and is incident on the cylindrical parabolic block 30. Light raysinternally reflected by the cylindrical parabolic mirror 20 areprojected onto the lighting region 104 from the cylindrical parabolicblock exit surface 32 as substantially parallel light rays.

It is possible to emit light rays without changing the angle of thelight rays reflected by the cylindrical parabolic mirror 20 by formingthe cylindrical parabolic block exit surface 32 into a prism shapecomprising a surface substantially parallel to and a surfacesubstantially orthogonal to the light rays reflected by the cylindricalparabolic mirror 20.

Accordingly, with this composition, positioning the emission exitpositions of the light guide plate and the parabolic mirror is possibleby integrated formation, and it is possible to eliminate variancescaused by assembly.

Ninth Preferred Embodiment

FIG. 19 is an sub-scanning direction cross-sectional view of a lightingunit according to a ninth preferred embodiment of the present invention.In the ninth preferred embodiment of the present invention, an LEDsubstrate 230 comprises a reflective sheet 232 that is all or a portionof the region in which LED chips 210 are not mounted on the surface inwhich the LED chips 210 are mounted. Through this composition, it ispossible to guide a portion of the light hitting the LED substrate 230to the lighting region 104, such as lighting light rays 106 from the LEDlight-emission region not at the focal position of the cylindricalparabolic mirror 20, out of light emitted from the LED chips 210, so itis possible to efficiently light a document.

Here, it would be fine for the reflective sheet 232 to reflect thewavelength of light emitted from the LED chips 210, and it is possibleto use a metal plate such as an aluminum plate and/or the like, or aresin scattering sheet and/or the like. When a metal plate such as analuminum plate and/or the like is used, it is possible for this to alsobe used as a heat-radiating body that dissipates heat generated from theLED chips 210.

Tenth Preferred Embodiment

FIG. 20 is a perspective view of a lighting unit according to a tenthpreferred embodiment of the present invention. The lighting unitaccording to the tenth preferred embodiment is provided with areflective mirror 300 at both ends of the cylindrical parabolic mirror20 in the main scanning direction. The cylindrical parabolic mirror 20does not have curvature in the main scanning direction. Consequently,when there is no reflective minor 300, the portion of the light raysemitted from the LED array 220 in the main scanning direction progresseswithout refracting, and progresses to the outside of the lighting unit 2from the end surfaces of the cylindrical parabolic mirror 20 in the mainscanning direction. As a result, these light rays reach the outside ofthe scan line 8 of the document 7 (see FIG. 1) in the main scanningdirection and are not effectively utilized as lighting light. Hence, byproviding the reflective mirror 300, light progressing to the outside ofthe cylindrical parabolic mirror 20 in the main scanning direction isreflected and through this it is possible to effectively utilize thelight as lighting light by returning a portion of the light to the scanline 8 of the document 7.

FIG. 21 is a drawing showing the illumination distribution at the mainscanning direction end according to the tenth preferred embodiment ofthe present invention. In this drawing, the horizontal axis is the mainscanning direction and shows the positions of the LED 210 a of thecorresponding LED array 220 and the end LED 210 b positioned at the mainscanning direction end. When there is no reflective minor 300, because alarge amount of light leaks to the outside from the end LED 210 b,illumination in the main scanning direction decreases toward the end tothe inside of the end LED 210 b. On the other hand, when there is areflective mirror 300, it is possible to increase the lighting lightamount at the main scanning direction end by reflecting lightprogressing to the outside in the main scanning direction. As a result,by providing the reflective mirror 300, it is possible to lengthen theregion where the main scanning direction illumination is constant toclose to the end LED 210 b.

Accordingly, through this composition it is possible to increase thelighting light amount of the main scanning direction end, and thus it ispossible to effectively shorten the length of the lighting unit in themain scanning direction.

Eleventh Preferred Embodiment

FIG. 22 is a perspective view of an image scanning device according toan eleventh preferred embodiment of the present invention. In addition,FIG. 23 is an sub-scanning direction cross-sectional view of a lightingunit according to the eleventh preferred embodiment of the presentinvention. The image scanning device according to the eleventh preferredembodiment of the present invention is the lighting unit of the firstpreferred embodiment of the present invention, provided withheat-radiating plates. With this preferred embodiment, plate-shapedheat-radiating plates 50 formed of metal such as aluminum on theopposite surface as the mounting surface of the LED chips 210 of the LEDarray 230 are positioned adhered to the LED substrate, as shown in FIGS.22 and 23. In addition, the cylindrical parabolic mirror 20, the LEDsubstrate 230 and the heat-radiating plates 50 are joined into one bodyby joining screws 51.

As shown in FIG. 22, the image scanning device according to the eleventhpreferred embodiment comprises imaging optical systemposition-determining protrusions 1 a, lighting systemposition-determining protrusions 50 a, imaging optical systemposition-determining holes 52 a and lighting system position-determiningholes 52 b. The imaging optical system position-determining protrusions1 a are provided in the imaging optical system 1. The lighting systemposition-determining protrusions 50 a are provided in the heat-radiatingplates 50. The imaging optical system position-determining holes 52 aand the lighting system position-determining holes 52 b are provided instructural support plates 52. The imaging optical systemposition-determining protrusions 1 a interlock into the imaging opticalsystem position-determining holes 52 a, and the lighting systemposition-determining protrusions 50 a interlock into the lighting systemposition-determining holes 52 b. Through this, the imaging opticalsystem 1 and the lighting unit 2 are anchored.

The heat-radiating plates 50 are adhered and attached to the LEDsubstrate 230 on the surface opposite the mounting surface of the LEDchips 210 of the LED substrate 230. Through this, heat generated by theLED chips 210 is efficiently discharged to the heat-radiating plates 50and increases in the temperature of the LED chips 210 are controlled. Asa result, stable operation of the lighting unit and the image scanningdevice becomes possible.

In addition, only a portion of the heat-radiating plates 50 abuts thehousing and half is separated from the housing, so that heat from theLED chips 210 does not reach the housing. Accordingly, light receptorsprovided in the bottom of the housing do not experience an increase intemperature, so it is possible for the light receptors to receive imageinformation from the document 7 with good sensitivity.

It would be fine for the heat-radiating plates 50 of the eleventhpreferred embodiment of the present invention to be provided in thelighting unit 2 of each of the second through tenth preferredembodiments of the present invention. Through this, similar efficacy isobtained.

Twelfth Preferred Embodiment

FIGS. 24 and 25 are respectively sub-scanning direction cross-sectionalviews of a lighting unit and an image scanning device provided with sucha lighting unit according to a twelfth preferred embodiment of thepresent invention. The image scanning device according to the twelfthpreferred embodiment comprises a top glass sheet 3, a lighting unit 2,first lens mirrors 507, flat mirrors 508, apertures 509, openings 510,second lens mirrors 511, sensor ICs 512, a first sensor substrate 513 a,a second sensor substrate 513 b, signal processing ICs (ASIC) 514,electronic components 515, a housing 516 and a bottom plate 517.

The top glass sheet 3 is a transparent glass plate that supports adocument 7 such as literature, media and/or the like. The lighting unit2 is the same as the lighting unit 2 according to the eleventh preferredembodiment, is a unit for accomplishing linear lighting on the surfaceof the document, and comprises LED chips 210, an LED substrate 230,heat-radiating plates 50 and a cylindrical parabolic mirror 20.

The LED chips 210 are light sources for shining light. The LED substrate230 is a substrate to which the LED chips 210 are anchored and which isprovided with wiring for supplying electric current to the LED chips210. The heat-radiating plates 50 receive heat generated by the LEDchips 210 via the LED substrate 230 and dissipate this heat into theair. The cylindrical parabolic mirror 20 has a mirror surface thatcauses light generated by the LED chips 21 in the direction of thedocument supported by the top glass sheet 3 to be reflected asapproximately parallel light.

The first lens mirrors (also called the first lenses) 507 are concavefirst lens mirrors that receive divergent light from the document 7. Theflat mirrors 508 receive approximately parallel light from the firstlenses 507 and reflect this light. The apertures 509 receiveapproximately parallel light from the flat mirrors 508, block light atthe periphery and restrict the light passing through. The openings 510are provided on the surface of the apertures 509 or close thereto andare a part in which is provided an opening through which light receivedby the apertures 509 is allowed to pass. The second lens mirrors (alsocalled the second lenses) 511 are concave second lens mirrors forreceiving and condensing light passing through the apertures 509.

The second ICs 512 (also called light receivers) receive light reflectedfrom the second lens mirrors 511 that has passed through the openings510, and are sensor ICs (Integrated Circuits) having a MOS semiconductorcomposition comprising a photoelectric conversion circuit foraccomplishing photoelectric conversion and a driver. The first sensorsubstrate 513 a and the second sensor substrate 513 b are sensorsubstrates on which the sensor ICs 512 are mounted, and are respectivelypositioned lined up in the sub-scanning direction, as shown in FIG. 25.The signal processing ICs (ASIC) 514 are ICs for accomplishing signalprocessing on signals photoelectrically converted by the sensor ICs 512.The electronic components 515 are capacitors, resistors and/or the likemounted on the sensor substrates 513. The housing 516 is a hollow memberto which the imaging optical system that is the imaging means comprisingthe sensor ICs and mirrors is anchored. The bottom plate 517 is aplate-like member covering the bottom opening of the housing 516 and towhich the lenses and housing 516 are anchored.

The action of the optical system of the image scanning device accordingto the twelfth preferred embodiment of the present invention will beexplained. Light from the LED chips 210 is reflected by the cylindricalparabolic mirror 20 and shines on the document 7 as approximatelyparallel light. Scattered light reflected by the document 7 is inclinedto one side in the sub-scanning direction (in the leftward direction inFIG. 25) and is reflected as collimated light. Light from the first lens507 is reflected to the flat mirror 508 inclined to one side in thesub-scanning direction. Light from the flat mirror 508 shines on thewindow (opening 510) of the aperture 509 as approximately parallel lightrays. Furthermore, light radiating from the window 510 is reflected tothe second lens 511 inclined to one side in the sub-scanning direction,and because this light is incident on the sensor IC 512 for each beam,the image information is imaged as an inverted image on thelight-receiving surface of the sensor IC 512.

Scattered light shining from the left-side lighting unit 2 and reflectedby the document 7 that is the subject of illumination is inclined towardthe other side (the left direction in FIG. 25) in the sub-scanningdirection, and is incident on the sensor IC 512 on the first sensorsubstrate 513 a. Scattered light shining from the right-side lightingunit 2 and reflected by the document 7 that is the subject ofillumination follows a light path symmetrical to the light path shown inFIG. 25 on a plane orthogonal to the sub-scanning direction and isincident on the sensor IC 512 on the second sensor substrate 513 b.Consequently, the light path incident on the sensor IC 512 mounted onthe first sensor substrate 513 a and the light path incident on thesensor IC 512 mounted on the second sensor substrate 513 b do notintersect and thus it is possible to prevent light ray interference inthe light path.

In the twelfth preferred embodiment of the present invention, thelighting unit 2 explained in the eleventh preferred embodiment of thepresent invention is used, but similar efficacy and results are obtainedby using the lighting unit explained in the first through tenthpreferred embodiments of the present invention.

Having described and illustrated the principles of this application byreference to one or more preferred embodiments, it should be apparentthat the preferred embodiments may be modified in arrangement and detailwithout departing from the principles disclosed herein and that it isintended that the application be construed as including all suchmodifications and variations insofar as they come within the spirit andscope of the subject matter disclosed herein.

This application claims the benefit of priority based on Japanese PatentApplication No. 2011-234079, filed on Oct. 25, 2011, the entiredisclosure of which is incorporated by reference herein.

REFERENCE SIGNS LIST

1 Imaging optical system, 1 a Imaging optical systemposition-determining protrusion, 2 Lighting unit, 3 Top glass sheet, 4Substrate, 7 Document, 8 Scan line, 11 Main scanning direction, 12Sub-scanning direction, 13 Depth direction, 20 Cylindrical parabolicmirror, 21 Semi-cylindrical parabola y+, 22 Semi-cylindrical parabolay−, 23 Cylindrical parabola focal position, 24 Cylindrical parabolavertex, 25 Cylindrical parabola axial plane, 30 Cylindrical parabolicblock, 31 Cylindrical parabolic block incident surface, 32 Cylindricalparabolic block exit surface, 40 Imaging element, 50 Heat-radiatingplate, 50 a Lighting system position-determining protrusion, 51 Joiningscrew, 52 Structural support plate, 52 a Imaging optical systemposition-determining hole, 52 b Lighting system position-determininghole, 101 Imaging optical axis, 102 Lighting optical axis, 103 Lightinglight rays, 104 Lighting region, 105 Central axis in light-emissiondirection, 210 LED chip, 211 LED package, 212 Blue light-emitting diode,213 Yellow fluorescent material, 214 Blue light-emitting diode shortaxis, 215 Blue light-emitting diode long axis, 216 LED package topsurface, 217 Yellow fluorescent material strong light-emission region,218 LED light-emission region, 210, 210 a, 210 b LED chip, 220 LEDarray, 230 LED substrate, 231 Position-determining pin, 232 Reflectivesheet, 300 Reflective mirror, 400 Light guide plate, 401 Light guideplate incident surface, 402 Light guide plate exit surface, 403 Lightguide surface, 405 Light guide plate supporter, 410 Scatterer, 507Concave first lens mirror (first lens), 508 Flat minor, 509 Aperture,510 Opening, 511 Concave second lens mirror (second lens), 512 Sensor IC(light receiver), 513 Sensor substrate, 513 a First sensor substrate,513 b Second sensor substrate, 514 Signal processing IC (ASIC), 515Electronic components, 516 Housing, 517 Bottom plate

1. A lighting unit, comprising: a light source in which light-emittingelements are positioned in an array in a main scanning direction; alight source substrate that is a substrate extending in the mainscanning direction and comprises a light-emitting element mountingsection on which the light source is disposed and a non-light-emittingelement mounting section extending from the light-emitting elementmounting section in a direction orthogonal to the main scanningdirection; a parabolic mirror forming a shape in which a cylindricalparaboloid having curvature with respect to an sub-scanning directionhas been clipped by an axial plane that is perpendicular to the vertexof the cylindrical paraboloid in the main scanning direction, providedwith an anchoring section provided at the vertex of the cylindricalparaboloid and extending in the outside direction of the cylindricalparaboloid from the vertex, and projecting light emitted from the lightsource on an illumination region of an illuminated item; and aheat-radiating plate extending in the main scanning direction andpossessing a contact section that is in contact with the surfaceopposite the surface on which the light-emitting elements of the lightsource substrate are mounted, and a non-contact section; wherein thelight source is positioned so as to include the focal position of thecylindrical paraboloid in the light-emitting region of light, thecentral axis in the light-emitting direction of the light beingperpendicular to the axial plane; and the non-light-emitting elementmounting section of the light source substrate is interposed between thecontact section of the heat-radiating plate and the anchoring section ofthe parabolic mirror.
 2. The lighting unit according to claim 1,wherein: the light source is disposed in a surface facing the parabolicmirror on the light source substrate positioned parallel to the axialplane; and the light source substrate is anchored to the anchoringsection of the parabolic mirror by position-determining pins.
 3. Thelighting unit according to claim 1, wherein: the light source is a whiteLED that obtains white color by blending secondary light from a yellowfluorescent material, with a blue light-emitting diode as thelight-emitting element; and the short axis direction of the chips of theblue light-emitting diode is positioned so as to be parallel to the mainscanning direction.
 4. The lighting unit according to claim 1, wherein:the light source is a white LED that obtains white color by blendingsecondary light from a yellow fluorescent material, with a bluelight-emitting diode as the light-emitting element; and the area of theblue light-emitting diode chip on the vertex side of the parabolicmirror matches the focal position of the parabolic mirror.
 5. Thelighting unit according to claim 1, wherein the parabolic mirror isformed of a solid transparent material.
 6. The lighting unit accordingto claim 1, further comprising a light guide plate for guiding lightemitted from the light source; wherein the parabolic mirror shines lightvia the light guide plate emitted from the light source on theillumination region of the illuminated item.
 7. The lighting unitaccording to claim 6, wherein a scatterer for scattering light isdisposed between the light guide plate and the parabolic mirror.
 8. Thelighting unit according to claim 6, wherein the parabolic mirror isformed of a solid transparent material and is formed as a single bodywith the light guide plate.
 9. The lighting unit according to claim 1,wherein a reflective sheet is provided in an area other than the lightsource mounting area of the light source mounting surface of the lightsource substrate.
 10. The lighting unit according to claim 1, wherein areflective mirror is provided at the end of the parabolic mirror in themain scanning direction.
 11. The lighting unit according to claim 1,wherein the non-contact section of the heat-radiating plate extends in adirection parallel to the main scanning direction, continuing to thecontact section from the end side on the side opposite thelight-emitting element mounting section of the light source substrate.12. An image scanning device, comprising: the lighting unit according toclaim 1; an imaging optical system on which scattered light from lightreflected by a document in the illumination region of the illuminatedobject is incident, and which images an image of the illuminated item ina light receptor extending in the main scanning direction; and a housingfor housing or supporting the lighting unit, the imaging optical systemand the light receptor; being an image scanning device for scanning thedocument relative to the sub-scanning direction orthogonal to the mainscanning direction and obtaining image information of the illuminateditem; and wherein the lighting unit is positioned on both sides of theoptical axis of the imaging optical system in the main scanningdirection.
 13. The image scanning device according to claim 12, whereinthe lighting unit is positioned such that the illumination direction oflight exiting from the lighting unit is symmetrical with respect to theoptical axis of the imaging optical system.